package A2014;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class Test {
	static Map<Integer,Integer> lastIndex = new HashMap<Integer,Integer>();
	static ArrayList<Integer> arr = new ArrayList<Integer>();
	
	
	public static void main(String[] args) {
		Scanner sc =new Scanner(System.in);
		char c='9';
		int n=(11-1)>>1;
		System.out.println(n);
//		lastIndex.put(4, 4);
//		for (int i : lastIndex.values()) {
//			System.out.println(i);
//		}
//		for (int i : lastIndex.keySet()) {
//			System.out.println(i);
//		}
		
	}
}